The present invention relates to internal combustion engines and more particularly to apparatus for disabling selected cylinders of a multi-cylinder engine to achieve split engine operation.
Heretofore, various proposals have been made for operating an internal combustion engine on less than all of its complement of cylinders. Such operation is typically referred to as split engine operation. Under low and moderate load conditions, the efficiency and hence the rate of fuel consumption of an engine may be improved by reducing the number of operating cylinders. With an eight-cylinder engine, for example, once cruising speed is obtained, four cylinders are sufficient to maintain the cruise speed. Internal combustion engines operate most efficiently when they are under a load. By disabling selected cylinders, the remaining active cylinders are placed under a slightly increased load and therefore operate more efficiently. Overall fuel economy is increased.
Examples of prior apparatus for achieving split engine operation may be found in U.S. Pat. No. 2,878,798, entitled SPLIT ENGINE and issued on Mar. 24, 1959, to Dolza et al; U.S. Pat. No. 4,064,844, entitled APPARATUS AND METHOD FOR SUCCESSIVELY INACTIVATING THE CYLINDERS OF AN ELECTRONICALLY FUEL-INJECTED INTERNAL COMBUSTION ENGINE IN RESPONSE TO SENSED ENGINE LOAD and issued on Dec. 27, 1977, to Matsumoto et al; U.S. Pat. No. 4,064,861, entitled DUAL DISPLACEMENT ENGINE and issued on Dec. 27, 1977, to Schulz; and U.S. Pat. No. 4,080,948, entitled SPLIT ENGINE CONTROL SYSTEM and issued on Mar. 28, 1978, to Dolza, Sr.
Some of the prior devices are relatively complicated, must be incorporated into the original engine design or may not be added to existing engines without significant reworking and redesign of engine components. Other devices, such as those represented by the Schulz patent and the Dolza, Sr. patent noted above, may be added with little or no modification to the engine. The Schulz patent discloses a system including an auxiliary throttle assembly, an exhaust valve lock-up assembly and a micro-switch cam control assembly. The auxiliary throttle assembly is located in a modified passageway of the fuel intake manifold. A flexible cable connects a butterfly valve plate to the exhaust valve lock-up mechanism. Linkage also interconnects the butterfly valve with the micro-switch cam control. In operation, selective cylinders of the engine are disabled by moving the butterfly valve to a closed condition, thereby cutting off the air/fuel mixture to a particular cylinder. The exhaust valve for that same cylinder is held in an open position upon closure of the butterfly valve.
The control system disclosed in the Dolza, Sr. patent includes a shuttle valve structure positionable between the base of the engine carburetor and the partitioned inlet passages of an intake manifold. The shuttle valve is slidably disposed in a piston-like chamber. Intake manifold pressure or vacuum within the manifold passages leading to the "active" cylinders is sensed and used to control positioning of the shuttle valve.
A still further system which has recently been commercialized permits an eight-cylinder engine to run on eight, six or four cylinders, depending upon the load and power demand. This system employs a solenoid mechanism which disables the valves on the "inactive" cylinder so that the valves remain in a closed position.
A need exists for a relatively simple and easily manufactured device for achieving split engine operation and which is readily usable and incorporated into existing engines with minimal, if any, modification.